This invention relates to the field of avionics. In particular, this invention relates to a transponder lock that allows an aircraft transponder to continue transmitting an alerting code for the duration of an emergency.
An enormous amount of air traffic, carrying thousands upon thousands of human lives, moves across the skies around the world every day. Coordinating the safe takeoff, flight, and landing of each aircraft requires a sophisticated air traffic control network. In the United States, for example, the airspace is divided into 21 zone or centers, and each zone is divided into sectors. Within the zones are 50-mile diameter portions of airspace called TRACON (Terminal Radar Approach CONtrol) airspaces within which lie individual airports with 5-mile radius airspace.
An aircraft provides critical information during flight to help the air traffic control network coordinate air traffic. In particular, once an aircraft takes off, the pilot activates an aircraft transponder. The transponder detects incoming radar signals and, in response, broadcasts an encoded transponder signal in the return direction. The transponder signal typically includes the ATC assigned 4-digit transponder code (aircraft flight number) and altitude. As a result, radar units operated by air traffic controllers are able to display a symbol representing the aircraft, and the radar and air traffic controller may follow the plane throughout its flight.
Without the information provided by the transponder, air traffic control has reduced ability to determine where, how high, or how fast an aircraft is flying. Not only does the lack of transponder information present an unacceptable risk to those on board the aircraft, it also presents an unacceptable risk to passengers on other aircraft nearby, and individuals and property on the ground. In the past, however, aircraft transponders were unduly susceptible to manipulation.
The Sep. 11, 2001 terrorist attacks on the World Trade Center and the Pentagon provide a grim example of the vulnerability of aircraft transponders. According to a CBS News report (retrievable as of Apr. 3, 2002, for example at http://www.kutv.com/now/story/0,1597,311657-412,00.shtml), each transponder on board the four hijacked aircraft was simply shut off. As a result, air traffic control was deprived of vital information concerning where the planes were headed. It is conceivable, had air traffic control known where the planes were heading and how high they were flying, that warnings, evacuations, or other safety steps could have been initiated and directed to suspected target areas.
Another problem is that aircraft idle time caused by grounding the plane to retrofit improved avionics results in an enormous cost to the airline operating the aircraft. Furthermore, the specifications that govern aircraft design are often so strict that retrofitting improved avionics cannot be accomplished without significant investment of time, money, and resources.
A need has long existed for a mechanism that provides continued transponder operation in the event of emergency situations.
The transponder lock allows an aircraft transponder to continue transmitting, for example, an alerting code or other information or emergency indicia for the duration of an emergency. The transponder lock connects quickly and cleanly in-line with existing aircraft wiring, thereby minimizing aircraft downtime arising from installation of the transponder lock. The absence of installation complexity permits, for example, installing the transponder lock at an airport gate, rather than requiring an airline to incur substantial time and expense penalties arising from flying each aircraft to a remote retrofitting hangar.
Other features, apparatus, methods, and advantages of the present invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the present invention, and be represented by the accompanying drawings.